Alkylidene complexes of ruthenium containing n-heterocyclic carbene ligands; use as highly active, selective catalysts for olefin metathesis

ABSTRACT

The invention relates to a complex of ruthenium of the structural formula I, 
     
       
         
         
             
             
         
       
     
     where X 1  and X 2  are identical or different and are each an anionic ligand,
 
R 1  and R 2  are identical or different and can also contain a ring, and R 1  and R 2  are each hydrogen or/and a hydrocarbon group,
 
the ligand L 1  is an N-heterocyclic carbene and the ligand L 2  is an uncharged electron donor, in particular an N-heterocyclic carbene or an amine, imine, phosphine, phosphate, stibine, arsine, carbonyl compound, carboxyl compound, nitrile, alcohol, ether, thiol or thioether,
 
where R 1 , R 2 , R 3  and R 4  are hydrogen or/and hydrocarbon groups.
 
     The invention further relates to a process for preparing acyclic olefins having two or more carbon atoms or/and cyclic olefins having four or more carbon atoms from acyclic olefins having two or more carbon atoms or/and from cyclic olefins having four or more carbon atoms by an olefin metathesis reaction in the presence of at least one catalyst, wherein a complex is used as catalyst and R 1 , R ′2 , R ′3  and R ′4  are hydrogen or/and hydrocarbon groups.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/875,659, filed Sep. 3, 2010; which is a continuation of U.S. patentapplication Ser. No. 12/692,229, filed Jan. 22, 2010; which is acontinuation of U.S. patent application Ser. No. 11/021,967, filed Dec.23, 20004, which is a divisional of U.S. patent application Ser. No.10/630,551, filed Jul. 29, 2003; which is a divisional of U.S. patentapplication Ser. No. 09/647,742, filed Nov. 27, 2000 now U.S. Pat. No.6,635,768; which is a National stage of International Application No.PCT/EP99/01785, filed on Mar. 18, 1999; which claims benefit to GermanApplication Number 198 15 275.2, filed Apr. 6, 1998, all of which areincorporated herein by reference in their entirety for all usefulpurposes.

The invention relates to alkylidene complexes of ruthenium containingN-heterocyclic carbene ligands and a process for preparing olefins byolefin metathesis from acyclic olefins having two or more carbon atomsor/and from cyclic olefins having four or more carbon atoms using atleast one of these alkylidene complexes as catalyst.

C—C coupling reactions catalyzed by transition metals are among the mostimportant reactions of organic synthetic chemistry. In this context,olefin metathesis makes a significant contribution, since this reactionenables by-product-free olefins to be synthesized. Olefin metathesis hasnot only a high potential in the area of preparative, organic synthesis(RCM, ethenolysis, metathesis of acyclic olefins) but also in polymerchemistry (ROMP, ADMET, alkyne polymerization).

Since its discovery in the 1950s, a number of industrial processes havebeen able to be realized. Nevertheless, olefin metathesis has developedinto a broadly applicable synthetic method only recently due to thediscovery of new catalysts (J. C. Mol in: B. Cornils, W. A. Het-unarm:Applied Homogeneous Catalysis with Organometallic Compounds, VCH,Weinheim, 1996, p. 318-332; M. Schuster, S. Blechert, Angew. Chem. 1997,109, 2124-2144; Angew, Chem. Int. Ed. Engl. 1997, 36, 2036-2056).

Numerous, fundamental studies have made important contributions to theunderstanding of this transition metal-catalyzed reaction in which anexchange of alkylidene units between olefins occurs. The generallyaccepted mechanism involves metal-alkylidene complexes as activespecies. These react with olefins to form metallacyclobutaneintermediates which undergo cycloreversion to once again form olefinsand alkylidene complexes. The isolation of metathesis-active alkylideneand metallacyclobutane complexes supports these mechanistic hypotheses.

Numerous examples may be found, in particular, in the coordinationchemistry of molybdenum and tungsten. Specifically the work of Schrockgave well-defined alkylidene complexes whose reactivity can becontrolled (J. S. Murdzek, R. R. Schrock, Organometallics 1987, 6,1373-1374). The introduction of a chiral ligand sphere in thesecomplexes made possible the synthesis of polymers having a hightacticity (K. M. Totland, T. J. Boyd, G. C. Lavoie, W. M. Davis, R. R.Schrock, Macromolecules 1996, 29, 6114-6125). Chiral complexes of thesame structural type have also been used successfully in ring-closingmetathesis (O. Fujimura, F. J. d. L. Mata, R. H. Grubbs, Organometallics1996, 15, 1865-1871). However, the high sensitivity toward functionalgroups, air and water is a drawback.

Recently, phosphine-containing complexes of ruthenium have becomeestablished (R. H. Grubbs, S. T. Nguyen, L. K. Johnson, M. A. Hillmyer,G. C. Fu, WO 96/04289, 1994; P. Schwab, M. B. France, J. W. Ziller, R.H. Grubbs, Angew. Chem., 1995, 107, 2119-2181; Angew. Chem. Int. Ed.Engl. 1995, 34, 2039-2041). Owing to the electron-rich, “soft” characterof later transition metals, these complexes have a high tolerance towardhard, functional groups. This is demonstrated, for example, by their usein natural product chemistry (RCM of dienes) (Z. Yang, Y. He, D.Vourloumis, H. Vallberg, K. C. Nicolaou, Angew. Chem. 1997, 109,170-172; Angew. Chem., Int. Ed. Engl. 1997, 36; 166-168; D. Meng, P.Bertinato, A. Balog, D. S. Su, T. Kamenecka, E. J. Sorensen, S. J.Danishefsky, J. Am. Chem. Soc. 1997, 119, 2733-2734; D. Schinzer, A.Limberg, A. Bauer, O. M. Böhm, M. Cordes, Angew. Chem. 1997, 109,543-544; Angew. Chem., Int. Ed. Engl. 1997, 36, 523-524; A. Fürstner, K.Langemann, J. Am. Chem. Soc. 1997, 119, 9130-9136).

However, the range of variation of the phosphine ligands used is veryrestricted due to steric and electronic factors. Only strongly basic,bulky alkylphosphines such as tricyclohexylphosphine,triisopropylphosphine and tricyclopentylphosphine are suitable for themetathesis of acyclic olefins and relatively unstrained ring systems.Accordingly, the reactivity of these catalysts cannot be adjusted.Chiral complexes of this structural type have also not been able to beobtained.

For these reasons, it is an object of the invention to develop tailoredmetathesis catalysts which have a high tolerance toward functionalgroups as a result of a variable ligand sphere and which allow fineadjustment of the catalyst for specific properties of different olefins.

This object is achieved according to the invention by a complex ofruthenium of the structural formula I,

where X¹ and X² are identical or different and are each an anionicligand,R¹ and R² are identical or different and can also contain a ring, and R¹and R² are each hydrogen or/and a hydrocarbon group, where thehydrocarbon groups are identical or different and are selectedindependently from among straight-chain, branched, cyclic or/andnoncyclic radicals from the group consisting of alkyl radicals havingfrom 1 to 50 carbon atoms, alkenyl radicals having from 1 to 50 carbonatoms, alkynyl radicals having from 1 to 50 carbon atoms, aryl radicalshaving from 1 to 30 carbon atoms and silyl radicals,where one or more of the hydrogen atoms in the hydrocarbon or/and silylgroups can be replaced independently by identical or different alkyl,aryl, alkenyl, alkynyl, metallocenyl, halogen, nitro, nitroso, hydroxy,alkoxy, aryloxy, amino, amido, carboxyl, carbonyl, thio or/and sulfonylgroups,the ligand L¹ is an N-heterocyclic carbene of the formulae II-V and theligand L² is an uncharged electron donor, in particular anN-heterocyclic carbene of the formulae II-V or an amine, imine,phosphine, phosphite, stibine, arsine, carbonyl compound, carboxylcompound, nitrile, alcohol, ether, thiol or thioether,

where R¹, R², R³ and R⁴ the formulae II, III, IV and V are identical ordifferent and are each hydrogen or/and a hydrocarbon group,where the hydrocarbon groups comprise identical or different, cyclic,noncyclic, straight-chain or/and branched radicals selected from thegroup consisting of alkyl radicals having from 1 to 50 carbon atoms,alkenyl radicals having from 1 to 50 carbon atoms, alkynyl radicalshaving from 1 to 50 carbon atoms and aryl radicals having from 1 to 30carbon atoms, in which at least one hydrogen may be replaced byfunctional groups, and where one or both of R³ and R⁴ may be identicalor different halogen, nitro, nitroso, alkoxy, aryloxy, amido, carboxyl,carbonyl, thio or/and sulfonyl groups.

The alkyl radicals, alkenyl radicals or alkynyl radicals in the formulaeI to V preferably have from 1 to 20 carbon atoms, particularlypreferably from 1 to 12 carbon atoms.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates the yield % versus t/min for compounds A and B in aring-opening metathesis polymerization of 1,5-cyclooctadiene and

FIG. 2 illustrates the yield % versus t/min for compounds A and B in aring-opening metathesis polymerization of cyclooctene.

The complexes of the invention are highly active catalysts for olefinmetathesis. They are particularly inexpensive. In olefin metathesis, thecatalysts of the invention display not only a high tolerance toward avariety of functional groups but also a wide range of possiblevariations in the ligand sphere. Variation of the preparatively readilyobtainable N-heterocyclic carbene ligands enables activity andselectivity to be controlled in a targeted manner and, in addition,chirality can be introduced in a simple way.

The anionic ligands X¹ and X² of the complex of the of invention, whichare identical or different, are preferably each halide, pseudohalide,tetraphenylborate, perhalogenated, tetraphenylborate, tetrahaloborate,hexahalophosphate, hexahaloantimonate, trihalomethanesulfonate,alkoxide, carboxylate, tetrahaloaluminate, tetracarbonylcobaltate,hexahaloferrate (III), tetrahaloferrate (III) or/and tetrahalopalladate(II), with preference being given to halide, pseudohalide,tetraphenylborate, perfluorinated tetraphenylborate, tetrafluoroborate,hexafluorophosphate, hexafluoroantimonate, trifluorotnethanesulfonate,alkoxide, carboxylate, tetrachloroaluminate, tetracarbonylcobaltate,hexafluoroferrate (III) tetrachloroferrate (III) or/andtetrachloropalladate (II) and preferred pseudohalides being cyanide,thiocyanate, cyanate, isocyanate and isothiocyanate.

In the formulae II, III, IV and V, some or all of the hydrogen in thehydrocarbon groups R¹, R², R³ and R⁴ can be replaced independently byidentical or different halogen, nitro, nitroso, hydroxy, alkoxy,aryloxy, amino, amido, carboxyl, carbonyl, thio, sulfonyl or/andmetallocenyl groups. In these formulae, R³ and R⁴ can form a fused-onring system.

The ligands L¹ and L² of the complex of the structural formula I canform a chelating ligand of the formula VI

L¹-Y-L²  VI

where the bridges Y can comprise cyclic, noncyclic, straight-chainor/and branched radicals selected from the group consisting of alkyleneradicals having from 1 to 50 carbon atoms, alkenylene radicals havingfrom 1 to 50 carbon atoms, alkynylene radicals having from 1 to 50carbon atoms, arylene radicals having from 1 to 30 carbon atoms,metallocenylene, borylene and silylene radicals in which one or morehydrogens may be replaced independently by identical or different alkyl,aryl, alkenyl, alkynyl, metallocenyl, halo, nitro, nitroso, hydroxy,alkoxy, aryloxy, amino, amido, carboxyl, carbonyl, thio or/and sulfonylgroups, preferably alkyl, aryl or/and metallocenyl groups.

The ligands of the formulae II, III, IV, V or/and VI can have central,axial or/and planar chirality.

In the structural formula I of the complex, R¹ and R² are preferablyhydrogen, substituted or/and unsubstituted alkyl, alkenyl or/and arylradicals, X¹ and X² are preferably halide, alkoxide or/and carboxylateions and L¹ and L² are preferably each an N-heterocyclic carbene of theformula II.

The complexes are usually synthesized by ligand replacement incorresponding phosphine complexes. Two phosphine ligands can be replacedselectively in accordance with the reaction equation (1) or only one canbe replaced in accordance with reaction equation (2). In the case ofsingle replacement, the second phosphine can be replaced selectively byanother electron donor, e.g. pyridine, phosphine, N-heterocycliccarbene, phosphite, stilbene, arsine, in accordance with reactionequation (3).

In particular, this route makes it possible for the first time toprepare chiral, metathesis-active catalysts based on ruthenium (examplecomplexes 2 and 3).

The complexes of the invention are found to be extremely efficientcatalysts in olefin metathesis. The excellent metathesis activity isdemonstrated in the examples by means of a number of examples ofdifferent metathesis reactions.

The present invention therefore also encompasses processes for allolefin metathesis reactions such as ring-opening metathesispolymerization (ROMP), metathesis of acyclic olefins, ethenolysis,ring-closing metathesis (RCM), acyclic diene metathesis polymerization(ADMET) and depolymerization of olefin polymers. The high stability andtolerance of the complexes of the invention toward functional groups; inparticular alcohol, amine, thiol, ketone, aldehyde, carboxylic acid,ester, amide, ether, silane, sulfide and halogen groups, makes itpossible for such functional groups to be present during the metathesisreaction.

The object of the invention is also achieved by a process for preparingacyclic olefins having two or more carbon atoms or/and cyclic olefinshaving four or more carbon atoms, in each case of the formula VII

from acyclic olefins having two or more carbon atoms or/and from cyclicolefins having four or more carbon atoms, in each case corresponding tothe formula VII by an olefin metathesis reaction in the presence of atleast one catalyst, whereina catalyst as claimed in any one of claims 1 to 7 is used and R′¹, R′²,R′³ and R′⁴ in the formula VII are hydrogen or/and hydrocarbon groups,where the hydrocarbon group is each selected independently from amongstraight-chain, branched, cyclic or/and noncyclic radicals of the groupconsisting of alkyl radicals having from 1 to 50 carbon atoms, alkenylradicals having from 1 to 50 carbon atoms, alkynyl radicals having from1 to 50 carbon atoms, aryl radicals having from 1 to 30 carbon atoms,metallocenyl or/and silyl radicals, in which one or more hydrogens maybe replaced by a functional group,where one or more of R′¹, R′², R′³ and R′⁴ may independently beidentical or different halogen, nitro, nitroso, hydroxy, alkoxy,aryloxy, amino, amido, carboxyl, carbonyl, thio, sulfonyl or/andmetallocenyl groups.

The olefins used preferably contain one or more double bonds. Inparticular, R′¹, R′², R′³ and R′⁴ in the olefins of the formula VII tobe prepared form, in pairs, one or more identical or different rings.

Preferably, some or all of the hydrogen atoms in the hydrocarbon groupsR′¹, R′², R′³ and R′⁴ of the olefins of the formula VII to be preparedare replaced independently by identical or different halogen, silyl,nitro, nitroso, hydroxy, alkoxy, aryloxy, amino, amido, carboxyl,carbonyl, thio, sulfonyl or/and metallocenyl groups.

The process of the invention can be carried out in the presence orabsence of solvents, but preferably in the presence of organic solvents.The process of the invention can advantageously be carried out withaddition of a Brönsted acid, preferably HCl, HBr, HI, HBF₄, HPF₆ or/andtrifluoroacetic acid, or/and with addition of a Lewis acid, preferablyBF₃, AlCl₃ or/and ZnI₂.

Surprisingly, this makes it possible for the first time to tailor a widevariety of olefins individually to different properties on the basis ofsmall variations in the catalysis conditions or/and the catalysts, sincethe process of the invention for preparing olefins has an unexpectedlyhigh tolerance toward functional groups.

EXAMPLES

The following examples illustrate the invention but do not restrict itsscope.

1) Preparation of the Complex of the Invention General Procedure:

1 mmol of (PPh₃)₂Cl₂Ru(═CHPh) was dissolved in 20 ml of toluene andadmixed with a solution of 2.2 equivalents of the appropriateimidazolin-2-ylidene in 5 ml of toluene. The reaction solution wasstirred at room temperature RT for 45 minutes, subsequently evaporatedto about 2 ml and the crude product was precipitated using 25 ml ofpentane. The crude product was taken up in 2 ml of toluene andprecipitated using 25 ml of pentane a number of times. The residue wasextracted with toluene, the solution was evaporated to dryness, washedtwice with pentane and dried for a number of hours in a high vacuum.

The data from low-temperature NMR spectra are mostly reported forcharacterization, since the spectra at room temperature sometimes didnot give all the information because of dynamic effects.

The following compounds are prepared by the abovedescribed generalprocedure:

1a) Benzylidenedichlorobis(1,3-diisopropylimidazolin-2-ylidene)ruthenium

Complex 1:

Yield: 487 mg (0.86 mmol=86% of theory)

Elemental analysis EA for C₂₅H₃₈Cl₂N₄Ru (566.58):

found C, 53.21; H, 6.83; N, 9.94.

calculated C, 53.00; H, 6.76; N, 9.89.

¹H-NMR (CD₂Cl₂/200K): δ 20.33 (1H, s, Ru═CH), 8.25 (2H, d, ³J_(HH)=7.6Hz, o-H of C₆H₅) 7.63 (1H, t, ³J_(HH)=7.6 Hz, p-H of C₆H₅), 7.34 (2H, t,m-H of C₆H₅, ³J_(HH)=7.6 Hz), 7.15 (2H, br, NCH), 7.03 (2H, br, NCH),5.97 (2H, spt, ³J_(HH)=6.4 Hz, NCHMe₂), 3.73 (2H, spt, ³J_(HH)=6.4 Hz,NCHMe₂), 1.64 (12H, d, ³J_(HH)=6.4 Hz, NCHMe₂), 1.11 (6H, d, ³J_(HH)=6.4Hz, NCHMe₂), 0.75 (6H, d, ³J_(HH)=6.4 Hz, NCHMe₂).

¹³C-NMR (CD₂Cl₂/200K): δ 295.6 (Ru═CH), 183.5 (NCN), 151.6 (ipso-C ofC₆H₅), 129.5, 128.6 and 128.1 (o-C, m-C and p-C of C₆H₅), 118.1 and117.2 (NCH), 52.1 and 50.1 (NCHMe₂), 24.5, 23.8, 23.8 and 22.4 (NCHMe₂).

1b)Benzylidenedichlorobis(1,3-di((R)-1′-phenylethyl)-imidazolin-2-ylidene)ruthenium

Complex 2:

Yield: 676 mg (0.83 mmol=83% of theory)

EA for C₄₅H₄₆Cl₂N₄Ru (814.86)

found C, 66.48; H, 5.90; N, 6.73.

calc. C, 66.33; H, 5.69; N, 6.88.

¹H-NMR (CD₂Cl₂/200K): δ 20.26 (1H, s, Ru═CH), 8.13 (2H, br, o-H C₆H₅),7.78-6.67 (29H, of which 2m-H and 1p-H of C₆H₅, 20H of NCHMePh, 2H ofNCHMePh and 4H of NCH), 4.91 (2H, m, NCHMePh), 1.84 (3H, d, ³J_(HH)=6.6Hz, NCHMePh), 1.81 (3H, d, ³J_(HH)=6.6 Hz, NCHMePh), 1.51 (3H, d,³J_(HH)=6.6 Hz, NCHMePh), 1.21 (3H, d, ³J_(HH)=6.6 Hz, NCHMePh).

¹³C-NMR (CD₂C₂/200K): δ 294.7 (Ru═CH), 186.0 and 185.6 (NCN), 151.2(ipso-C of C₆H₅), 141.2, 140.3, 140.1 and 139.9 (ipso-C of NCHMePh),133.1-125.9 (o-C, m-C, p-C of C₆H₅ and NCHMePh), 120.5, 119.9, 119.2 and118.8 (NCH), 57.6, 57.4, 56.7 and 56.1 (NCHMePh), 22.2, 20.6, 20.4 and20.3 (NCHMePh).

1c)Benzylidenedichlorobis(1,3-di-((R)-1′-naphthyl-ethyl)imidazolin-2-ylidene)ruthenium

Complex 3:

Yield: 792 mg (0.78 mmol=78% of theory)

EA for C₆₁H₅₄Cl₂N₄Ru (1015.1):

found C, 72.34; H, 5.46; N, 5.45.

calc. C, 72.18; H, 5.36; N, 5.52.

¹H-NMR (CD₂Cl₂/260K): δ 20.90 (1H, s, Ru═CH), 8.99 (2H, br, o-H ofC₆H₅), 8.2-5.6 (39H, of which 2m-H and 1p-H of C₆H₅, 28H of NCHMeNaph,4H of NCH and 4H of NCHMeNaph), 2.5-0.8 (12H, m, NCHMeNaph).

¹³C-NMR (CD₂Cl₂/260K): δ 299.9 (Ru═CH), 187.2 and 184.7 (NCN), 152.0(ipso-C of C₆H₅), 136.0-124.0 (o-C, m-C, p-C of C₆H₅ and NCHMeNaph),121.7, 121.0, 119.9, and 118.9 (NCH), 56.7, 56.1, 55.0 and 54.7(NCHMeNaph), 24.7, 24.3, 21.0 and 20.0 (NCHMeNaph).

For the following complexes, slight deviations from the generalprocedure are necessary:

1d)(4-Chlorobenzylidene)dichlorobis(1,3-diisopropylimidazolin-2-ylidene)ruthenium

Complex 4:

1 mmol of (PPh₃)₂Cl₂Ru[═CH (p-C₆H₄Cl)] was used as starting material.The further procedure corresponded to the abovedescribed generalprocedure.

Yield: 535 mg (0.89 mmol=89% of theory)

EA for C₂₄H₃₈Cl₃N₄Ru (601.03):

found C, 48.13; H, 6.33; N, 9.24.

calc. C, 47.96; H, 6.37; N, 9.32.

¹H-NMR (CD₂Cl₂/200K): δ 20.33 (1H, s, Ru═CH), 8.25 (2H, d, ³J_(HH)=7.6Hz, o-H of C₆H₄Cl), 7.63 (1H, t, ³J_(HH)=7.6 Hz, m-H of C₆H₄Cl), 7.15(2H, br, NCH), 7.03 (2H, br, NCH), 5.97 (2H, spt, ³J_(HH)=6.4 Hz,NCHMe₂), 3.73 (2H, spt, ³J_(HH)=6.4 Hz, NCHMe₂), 1.64 (12H, d,³J_(HH)=6.4 Hz, NCHMe₂), 1.11 (6H, d, ³J_(HH)=6.4 Hz, NCHMe₂), 0.75 (6H,d, ³J_(HH)=6.4 Hz, NCHMe₂).

¹³C-NMR (CD₂Cl₂/200K): δ 295.6 (Ru═CH), 183.5 (NCN), 151.6 (ipso-C ofC₆H₄Cl), 134.3 (p-C of C₆H₄Cl), 128.6 and 128.1 (o-C and m-C of C₆H₄Cl),118.1 and 117.2 (NCH), 52.1 and 50.1 (NCHMe₂), 24.5, 23.8, 23.8 and 22.4(NCHMe₂).

1e)Benzylidenedichlorobis(1,3-dicyclohexylimidazolin-2-ylidene)ruthenium

Complex 5:

1 mmol of (PPh₃)₂Cl₂Ru(═CHPh) was dissolved in 25 ml of toluene andadmixed with a solution of 2.2 equivalents of1,3-dicyclohexylimidazolin-2-ylidene in 5 ml of toluene. The reactionsolution was stirred at RT for 45 minutes and subsequently freed of thesolvent. Unlike the general procedure, the crude product was purified byflash chromatography.

Yield: 305 mg (0.42 mmol=42% of theory).

EA for C₃₇H₅₄Cl₂N₄Ru (726.84):

found C, 61.23; H, 7.56; N, 7.87.

calc. C, 61.14; H, 7.49; N, 7.71.

¹H-NMR (CD₂Cl₂/298K): δ 20.45 (1H, s, Ru═CH), 8.31 (2H, d, ³J_(HH)=7.6Hz, o-H— of C₆H₅), 7.63 (1H, t, ³J_(HH)=7.6 Hz, p-H— of C₆H₅), 7.34 (2H,t, ³J_(HH)=7.6 Hz, m-H— of C₆H₅), 7.14 (2H, br, NCH), 7.00 (2H, br,NCH), 6.06 (2H, br, CH of NC₆H₁₁), 3.82 (2H, br, CH of NC₆H₁₁), 1.64(12H, br, CH₂ of NC₆H₁₁), 0.93 (12H, br, CH₂ of NC₆H₁₁).

¹³C-NMR (CD₂Cl₂/298K): δ 299.4 (Ru═CH), 182.9 (NCN), 152.0 (ipso-C ofC₆H₅), 131.1, 129.8 and 129.1 (o-C, m-C and p-C of C₆H₅), 118.3 and117.8 (br, NCH), 59.6 and 57.5 (br, CH of NC₆H₁₁), 35.7, 26.9 and 25.6(br, CH₂ of NC₆H₁₁)

1f) Benzylidenedichloro(1,3-di-tert-butylimidazolin-2-ylidene)(triphenylphosphine)ruthenium

Complex 6:

1 mmol of (PPh₃)₂Cl₂Ru(═CHPh) was dissolved in 20 ml of toluene andadmixed with a solution of 1.1 equivalents of1,3-di-tert-butylimidazolin-2-ylidene in 5 ml of toluene. The reactionsolution was stirred at RT for 30 minutes, subsequently evaporated toabout 2 ml and the crude product was precipitated using 25 ml ofpentane. The further work-up was carried out as described in the generalprocedure.

Yield; 493 mg (0.70 mmol=70% of theory)

EA for C₃₆H₄₁Cl₂N₂P₁Ru (704.69):

found C, 61.12; H, 5.55; N, 3.62; P, 4.59.

calc. C, 61.36; H, 5.86; N, 3.98; P, 4.38.

¹H-NMR (CD₂Cl₂/200K): δ 20.70 (1H, s, Ru═CH), 8.03 (2H, d, ³J_(HH)=7.6Hz, of C₆H₅), 7.50-6.95 (20H, of which 2m-H and 1p-H of C₆H₅, 15H ofPPh₃ and 2H of NCH), 1.86 (9H, s, NCMe₃), 1.45 (9H, s, NCMe₃).

¹³C-NMR (CD₂Cl₂/200K): δ 307.4 (br, Ru═CH), 178.3 (d, J_(PC)=86 Hz,NCN), 151.5 (d, J_(PC)=4.5 Hz, ipso-C of C₆H₅), 135.0 (m, o-C of PPh₃),131.9 (m, ipso-C of PPh₃), 130.2 (s, p-C of PPh₃), 129.5, 128.6 and128.1 (s, o-C, m-C and p-C of C₆H₅), 128.0 (m, m-C of PPh₃), 117.7 and117.6 (NCH), 58.7 and 58.5 (NCMe₃), 30.0 and 29.5 (NCMe₃).

³¹P-NMR (CD₂Cl₂/200K): δ 40.7 (s, PPh₃).

1 g)Benzylidenedichloro-(1,3-dicyclohexylimidazolin-2-ylidene)(tricyclohexylphosphine)ruthenium

A solution of 1.2 mmol of dicyclohexylimidazolin-2-ylidene is addeddropwise at −78° C. to 1 mmol of RuCl₂(PCy₃)₂(CHPh) in 100 ml of THF.The mixture is slowly warmed to room temperature over a period of 5hours and the solvent is subsequently removed. The crude product isextracted with a mixture of 2 ml of toluene and 25 ml of pentane and theproduct is precipitated from this solution at −78° C.

Yield: 0.80 mmol (80% of theory)

EA for C₄₀H₆₃Cl₂N₂PRu:

found C, 61.99; H, 8.20; N, 3.62. calc. C, 61.11; H, 8.29; N, 3.59.

¹H NMR (CD₂Cl₂/25° C.): δ=20.30 (1H, d, ³J_(PH)=7.4 Hz, Ru═CH), 8.33(2H, d, ³J_(HH)=7.4 Hz, o-H of C₆H₅), 7.62 (1H, t, ³J_(HH)=7.4 Hz, p-Hof C₆H₅), 7.33 (2H, t, ³J_(HH)=7.4 H₂, o-H of C₆H₅), 7.11 (1H, s, NCH),6.92 (1H, s, NCH), 5.97 (1H, m, CH of NC₆H₁₁), 3.36 (1H, m, CH ofNC₆H₁₁), 2.42 (3H, m, CH of PCy₃), 1.90-0.89 (50H, all m, CH₂ of NC₆H₁₁and PCy₃).

¹³C NMR (CD₂Cl₂/25° C.): d=298.7 (Ru═CH), 181.2 (d, J_(PC)=88 Hz, NCN),152.5 (ipso-C of C₅H₅), 130.8, 129.8, and 129.2 (o-C, m-C, and p-C ofC₆H₅), 118.9 and 118.0 (NCH), 59.5 and 57.7 (CH of NC₅H₁₁) 33.2 (d,J_(PC)=17 Hz, ipso-C of PCy₃), 29.9 (s, m-C of PCy₃), 26.8 (d,J_(PC)=3.7 Hz, o-C of PCy₃), 25.4 (s, p-C of PCy₃) 34.9, 33.3, 33.1,28.2, 28.1, and 25.7 (CH₂ of NC₆H₁₁).

³¹P NMR (CD₂Cl₂/25° C.) d=28.2.

1 h)Benzylidenedichloro(1,3-di-((R)-1′-phenylethyl)-imidazolin-2-ylidene)(tricyclohexylphosphine)ruthenium

A solution of 1.2 mmol of di-(R)-1′-phenylethylimidazolin-2-ylidene isadded dropwise at −78° C. to 1 mmol of RuCl₂(PCy₃)₂(CHPh) in 100 ml ofTHF. The mixture is slowly warmed to room temperature over a period of 5hours and the solvent is subsequently removed. The crude product isextracted with a mixture of 2 ml of toluene and 25 ml of pentane and theproduct is precipitated from this solution at −78° C.

Yield: 0.74 mmol (74% of theory)

EA for C₄₄H₅₉Cl₂N₂PRu:

calc. C, 64.53; H, 7.27; N, 3.42. found C, 64.58; H, 7.34; N, 3.44.

¹H NMR (CD₂Cl₂/25° C.): d 20.19 (1H, d, ³J_(PH)=4.5 Hz, Ru═CH),7.74-7.00 (15H, all m, CH of C₆H₅), (1H, m, NCHMePh), 6.73 (1H, s, NCH),6.70 (1H, s, NCH), 2.52 (1H, m, NCHMePh), 2.44 (3H, m, CH of PCy₃), 2.11(3H, d, ³J_(HH)=6.8 Hz, NCHMePh), 1.82-1.12 (30H, all m, CH₂ of PCy₃)1.35 (3H, d, ³J_(HH)=6.8 Hz, NCHMePh).

¹³C NMR (CD₂Cl₂/25° C.): δ=292.7 (Ru═CH), 183.4 (d, J_(PC)=78 Hz, NCN),151.8 (ipso-C of C₆H₅), 140.1 and 139.5 (ipso-C of NCHMEPh), 129.5,128.5, 128.3, 127.9, 127.5, 127.4, 127.2, 126.6, and 126.1 (o-C, m-C andp-C of C₆H₅) 119.8 and 118.4 (NCH), 57.4 and 56.2 (NCHMePh), 31.3 (d,J_(PC)=17 Hz, ipso-C of PCy₃), 29.0 (s, m-C of PCy₃), 28.9 (s, m-C ofPCy₃), 27.2 (d, J_(PC)=3.7 Hz, o-C of PCy₃), 27.0 (d, J_(PC)=3.7 Hz, o-Cof PCy₃), 25.8 (s, p-C of PCy₃) 21.7 and 20.3 (NCHMePh).

³¹P NMR (CD₂Cl₂/25° C.): δ 38.1.

1i)Benzylidenedichloro(1,3-di-((R)-1′-naphthylethyl)-imidazolin-2-ylidene)(tricyclohexylphosphine)ruthenium

A solution of 1.2 mmol of di-(R)-1′-naphthylethylimidazolin-2-ylidene isadded dropwise at −78° C. to 1 mmol of RuCl₂(PCy₃)₂(CHPh) in 100 ml ofTHF. The mixture is slowly warmed to room temperature over a period of 5hours and the solvent is subsequently removed. The crude product isextracted with a mixture of 2 ml of toluene and 25 ml of pentane and theproduct is precipitated from this solution at −78° C.

Yield: 0.72 mmol (72% of theory)

EA for C₅₂H₆₃Cl₂N₂PRu:

calc. C, 67.95; H, 6.91; N, 3.05. found C, 68.09; H, 7.02; N, 3.04.

¹H NMR (CD₂Cl₂/25° C.): δ 20.33 (1H, d, ³J_(HH)=5.4 Hz, Ru═CH), 8.88(2H, d, ³J_(HH)=8.0 Hz, o-H of C₆H₅) 7.94-6.96 (17H, all m, CH of C₆H₅),6.70 (1H, s, NCH), 6.61 (1H, s, NCH), 5.83 (1H, m, NCHMeNaph), 2.59 (1H,m, NCHMeNaph), 2.49 (3H, m, CH of PCy₃), 2.44 (3H, d, ³J_(HH)=6.8 Hz,NCHMeNaph), 1.95-1.01 (30H, all m, CH₂ of PCy₃) 1.54 (3H, d, ³J_(HH)=6.8Hz, NCHMeNaph).

¹³C NMR (CD₂Cl₂/25° C.): δ=298.4 (Ru═CH), 184.0 (d, J_(PC)=87 Hz, NCN),152.3 (ipso-C of C₆H₅), 138.3 and 137.6 (ipso-C of NCHMeNaph),134.3-122.9 (o-C, m-C, and p-C of C₆H₅, CHMeNaph) 120.6 and 119.5 (NCH),56.4 and 55.7 (NCHMeNaph), 32.5 (d, J_(PC)=17 Hz, ipso-C of PCy₂), 30.1(s, m-C of PCy₂), 30.0 (s, m-C of PCy₂), 28.1 (pseudo-t, J_(PC)=7.4 Hz,o-C of PCy₃), 26.8 (s, p-C of PCy₃) 24.0 and 22.7 (NCHMeNaph).

³¹P NMR (CD₂Cl₂/25° C.): δ=31.8.

2) Use of the Complex of the Invention in Olefin Metathesis

The following examples demonstrate the potential of the complexes of theinvention in olefin metathesis. The advantage of these complexes of theinvention compared to phosphine-containing complexes is the targeted andinexpensive variation of the radicals R on the nitrogen atoms of theN-heterocyclic, carbene ligands. This tailoring of the catalysts of theinvention on the basis of individual properties of the olefins to besubjected to metathesis enables both activity and selectivity of thereaction to be controlled.

2a) Ring-Opening Metathesis Polymerization (ROMP):

Norbornene, cyclooctene and functionalized norbornene derivatives serveas examples.

Typical Reaction Procedure for the Polymerization of Cyclooctene (orNorbornene):

410 μl (3.13 mmol) of cyclooctene were added to a solution of 3.6 mg(6.3 μmol) of 1 in 0.5 ml of methylene chloride. After about 10 minutes,a highly viscous gel which could no longer be stirred had formed. 1 mlof methylene chloride was added. This procedure was repeated wheneverthe stirrer was no longer able to operate (a total of 3 ml of methylenechloride). After 1 hour, 5 ml of methylene chloride to which smallamounts of tert-butyl ether and 2,6-di-tert-butyl-4-methylphenol hadbeen added were introduced. After a further 10 minutes, the solution wasslowly added dropwise to a large excess of methanol, the mixture wasfiltered and the solid was dried in a high vacuum for a number of hours.

Yield: 291 mg (2.64 mmol=84.3% of theory)

TABLE 1 Polymerization of norbornene and cyclooctene Ratio of Com-[monomer]/ Reaction Example plex Monomer [cat.] time t Yield 2.1a 1Norbornene 100:1 1 min 91% 2.1b 5 Norbornene 100:1 1 min 92% 2.1c 1Cyclooctene 500:1 1 h 84% 2.1d 1 Cyclooctene 500:1 2 h 97% 2.1e 5Cyclooctene 500:1 1 h 87%

Typical Reaction Procedure for the Polymerization of FunctionalizedNorbornene Derivatives:

The formula VIII shows the basic skeleton of the norbornene derivativesused in Table 2.

0.3 ml of a solution of 432 mg (3.13 mmol) of 5-carboxyl-2-norbornene(formula VIII with R═CO₂H) in methylene chloride was added to a solutionof 3.6 mg (6.3 μmol) of 1 in 0.2 ml of methylene chloride. After about10 minutes, a highly viscous gel which could no longer be stirred hadformed. A further 0.5 ml of methylene chloride was added. This procedurewas repeated whenever the stirrer was no longer able to operate. After 1hour, 5 ml of methylene chloride to which small amounts of tert-butylether and 2,6-di-tert-butyl-4-methylphenol had been added wereintroduced. After a further 10 minutes, the solution was slowly addeddropwise to a large excess of methanol, filtered and the solid was driedin a high vacuum for a number of hours.

Yield: 423 mg (3.06 mmol=98.1% of theory)

The reactions at 50° C. were carried out in an analogous manner indichloroethane instead of methylene chloride.

TABLE 2 Polymerization of functionalized norbornene derivatives RadicalR in formula Reaction Example Complex VIII T[° C.] time t Yield 2.1f 1O₂CCH₃ 25 30 min 99% 2.1g 1 CH₂OH 25 2 h 15% 2.1h 1 CH₂OH 50 2 h 18%2.1i 1 CHO 25 2 h 36% 2.1k 1 CHO 50 2 h 52% 2.1l 1 COCH₃ 25 2 h 42% 2.1m1 COCH₃ 50 2 h 67% 2.1n 1 CO₂H 25 2 h 98%

The polymerization of norbornene occurred in seconds. In thepolymerization of cyclooctene, virtually quantitative conversions wereobtained within one hour (Table 1). Differences in activity can bedetected by use of various complexes under dilute conditions anddemonstrate the dependence of the activity on the substitution patternof the carbene ligands used. The high stability and tolerance towardfunctional groups is demonstrated by the polymerization offunctionalized norbornene derivatives containing ester, alcohol,aldehyde, ketone or/and carboxylic acid groups (Table 2). Here, monomersof the formula VIII with R═CH₂OH, CHO and CO₂H were able to bepolymerized for the first time.

2.2) Ring-Closing Metathesis (RCM) of 1,7-octadiene:

Typical Reaction Procedure for RCM of 1,7-octadiene:

A solution of 3.6 mg (6.3 μmol) of 1 in 2 ml of dichloroethane wasadmixed with 46 μl (0.31 mmol) of 1,7-octadiene, and the reactionmixture was placed in an oil bath at 60° C. After one hour, the reactionmixture was analyzed by GC/MS.

TABLE 3 RCM of 1,7-octadiene (octadiene/catalyst = 50:1) ReactionExample Complex Solvent T[° C.] time t Yield 2.2a 1 Methylene chloride25 5.5 h 51% 2.2b 1 Methylene chloride 25  24 h 70% 2.2c 1Dichloroethane 60   1 h 99% 2.2d 2 Dichloroethane 60   1 h 99% 2.2e 3Dichloroethane 60   1 h 99% 2.2f 5 Dichloroethane 60   1 h 99%

The potential in ring-closing metathesis was illustrated by the reactionof 1,7-octadiene to form cyclohexene with liberation of ethylene (Table3). 1 gave a yield of 51% after 5.5 hours; at 60° C., all complexes ofthe invention used gave quantitative conversions.

2.3) Metathesis of Acyclic Olefins

A) Metathesis of 1-octene:

Typical Reaction Procedure for the Metathesis of 1-octane:

A solution of 3.6 mg (6.3 μmol) of 1 in 2 ml of dichloroethane wasadmixed with 49 μl (0.31 mmol) of 1-octene, and the reaction mixture wasplaced in an oil bath at 60° C. After 3 hours, the reaction mixture wasanalyzed by GC/MS.

TABLE 4 Homometathesis of 1-octene (octene/catalyst = 50:1) ReactionConversion Example Complex T[° C.] time t of 1-octene Selectivity^(a)2.3a 2 60 1 h 31% 98% 2.3b 2 60 2 h 58% 97% 2.3c 1 60 1 h 83% 73% 2.3d 160 3 h 97% 63% ^(a)The selectivity indicates the proportion of7-tetradecene compared to other metathesis products

B) Metathesis of Methyl Oleate:

Typical Reaction Procedure for the Metathesis of Methyl Oleate:

A solution of 3.6 mg (6.3 μmol) of 1 in 0.5 ml of dichloroethane wasadmixed with 1.06 ml (3.13 mmol) of methyl oleate, and the reactionmixture was placed in an oil bath at 60° C. for 15 hours. GC/MS analysisindicated the equilibrium of metathesis products shown in the reactionequation (7).

The metathesis of terminal and internal olefins was demonstrated bymeans of the homometathesis of 1-octene and methyl oleate. In themetathesis of methyl oleate as natural raw material, the thermodynamicequilibrium can virtually be reached within 15 hours using catalyst 1 atan olefin:catalyst ratio of 500:1. In the metathesis of 1-octene,7-tetradecene was not obtained as sole reaction product in all cases. Anisomerization of 1-octene to 2-octene detected by NMR spectroscopy andsubsequent olefin metathesis is responsible for this fact.Homometathesis and cross-metathesis of 1-octane and 2-octene gave notonly 7-tetradecene but also 6-tridecene as main by-product and smallamounts of 6-dodecene, 1-heptene and 2-nonene. The product distributionis strongly dependent on the catalyst used. In the case of 2,7-tetradecene was obtained virtually selectively; in contrast, the moreactive complex 1 gave 7-tetradecene in a selectivity of only 63% at ahigh conversion. The by-product obtained was essentially 6-tridecenefrom the cross-metathesis of 1-octene with 2-octene.

Ring-Opening Metathesis Polymerization (ROMP) of 1,5-cyclooctadiene

ROMP of 1,5-cyclooctadiene. NMR comparison of a ruthenium-dicarbenecomplex with a ruthenium-carbene phosphine complex. (T=25° C.; 1.70 μmolof catalyst in 0.55 ml of CD₂Cl₂; [1,5-cyclooctadiene]/[catalyst]—250:1)

The same applies to ROMP of cyclooctene:

ROMP of cyclooctadiene. NMR Kinetics of a ruthenium-dicarbene complexcompared to a ruthenium-carbene phosphine complex. (T=25° C.; 2.50 μmolof catalyst in 0.50 ml of CD₂Cl₂; [cyclooctadiene]/[catalyst]—250:1.

1. A complex of ruthenium of the structural formula I,

where X¹ and X² are identical or different and are each an anionicligand, R¹ and R² are identical or different and are each hydrogen or ahydrocarbon group, where the hydrocarbon groups are identical ordifferent and are selected independently from among straight-chain,branched, cyclic or noncyclic radicals from the group consisting ofalkyl radicals having from 1 to 50 carbon atoms, alkenyl radicals havingup to 50 carbon atoms, alkynyl radicals having up to 50 carbon atoms,aryl radicals having up to 30 carbon atoms and silyl radicals, or R¹ andR² form a ring, where one or more of the hydrogen atoms in thehydrocarbon or silyl groups or both the hydrocarbon and silyl group canbe replaced independently by identical or different alkyl, aryl,alkenyl, alkynyl, metallocenyl, halogen, nitro, nitroso, hydroxy,alkoxy, aryloxy, amino, amido, carboxyl, carbonyl, thio or sulfonylgroups, the ligand L¹ is an N-heterocyclic carbene of the formulae II-Vand the ligand L² is an N-heterocyclic carbene of the formulae III-V oran amine, imine, phosphine, phosphite, stibine, arsine, carbonylcompound, carboxyl compound, nitrile, alcohol, ether, thiol orthioether,

where R₁, R₂, R₃ and R₄ in the formulae II, III, IV and V are identicalor different and are each hydrogen or a hydrocarbon group, where thehydrocarbon groups comprise identical or different, cyclic, noncyclic,straight-chain or/and branched radicals selected from the groupconsisting of alkyl radicals having from 1 to 50 carbon atoms, alkenylradicals having up to 50 carbon atoms, alkynyl radicals having up to 50carbon atoms and aryl radicals having up to 30 carbon atoms, in which atleast one hydrogen may be replaced by functional groups, and where oneor both of R₃ and R₄ may be identical or different halogen, nitro,nitroso, alkoxy, aryloxy, amido, carboxyl, carbonyl, thio or sulfonylgroups. 2-3. (canceled)
 4. A complex as claimed in claim 1, wherein R³and R⁴ in the formulae II, III, IV and V form a fused-on ring system. 5.A complex as claimed in claim 1, wherein L¹ and L² form a chelatingligand of the formula VIL¹-Y-L²  VI where the bridges Y comprise cyclic, noncyclic,straight-chain or branched radicals selected from the group consistingof alkylene radicals having from 1 to 50 carbon atoms, alkenyleneradicals having up to 50 carbon atoms, alkynylene radicals having up to50 carbon atoms, arylene radicals having up to 30 carbon atoms,metallocenylene, borylene and silylene radicals in which one or morehydrogens may be replaced independently by identical or different alkyl,aryl, alkenyl, alkynyl, metallocenyl, halo, nitro, nitroso, hydroxy,alkoxy, aryloxy, amino, amido, carboxyl, carbonyl, thio or sulfonylgroups. 6-7. (canceled)
 8. A process for preparing acyclic olefinshaving two or more carbon atoms or cyclic olefins having four or morecarbon atoms, in each case of the formula VII

from acyclic olefins having two or more carbon atoms or from cyclicolefins having four or more carbon atoms, in each case corresponding tothe formula VII by an olefin metathesis reaction in the presence of atleast one catalyst comprising the complex as claimed in claim 1 and R′¹,R′², R′³ and R′⁴ in the formula VII are hydrogen or hydrocarbon groups,where the hydrocarbon groups are each selected independently from amongstraight-chain, branched, cyclic or noncyclic radicals of the groupconsisting of alkyl radicals having from 1 to 50 carbon atoms, alkenylradicals having up to 50 carbon atoms, alkynyl radicals having up to 50carbon atoms, aryl radicals having up to 30 carbon atoms, metallocenylor silyl radicals, in which one or more hydrogens may be replaced by afunctional group, where one or more of R′¹, R′², R′³ and R′⁴ mayindependently be identical or different halogen, nitro, nitroso,hydroxy, alkoxy, aryloxy, amino, amido, carboxyl, carbonyl, thio,sulfonyl or metallocenyl groups.
 9. (canceled)
 10. The process asclaimed in claim 8, wherein R′¹, R′², R′³ and R′⁴ in the olefins of theformula VII to be prepared form, in pairs, one or more identical ordifferent rings. 11-16. (canceled)
 17. A complex of ruthenium of thestructural formula I,

where X¹ and X² are identical or different and are each an anionicligand, R¹ and R² are identical or different and are each hydrogen or ahydrocarbon group, where the hydrocarbon groups are identical ordifferent and are selected independently from among straight-chain,branched, cyclic or noncyclic radicals from the group consisting ofalkyl radicals having from 1 to 50 carbon atoms, alkenyl radicals havingup to 50 carbon atoms, alkynyl radicals having up to 50 carbon atoms,aryl radicals having up to 30 carbon atoms and silyl radicals, or R¹ andR² form a ring, where one or more of the hydrogen atoms in thehydrocarbon or silyl groups or both the hydrocarbon and silyl group canbe replaced independently by identical or different alkyl, aryl,alkenyl, alkynyl, metallocenyl, halogen, nitro, nitroso, hydroxy,alkoxy, aryloxy, amino, amido, carboxyl, carbonyl, thio or sulfonylgroups or mixtures thereof, the ligand L¹ is an N-heterocyclic carbeneand the ligand L² is N-heterocyclic carbene of the formulae III-V or anamine, imine, phosphine, phosphite, stibine, arsine, carbonyl compound,carboxyl compound, nitrile, alcohol, ether, thiol or thioether andwherein formulae (III)-(V) are

where R₁, R₂, R₃ and R₄ in the formulae III, IV and V are identical ordifferent and are each hydrogen or a hydrocarbon group, where thehydrocarbon groups comprise identical or different, cyclic, noncyclic,straight-chain or/and branched radicals selected from the groupconsisting of alkyl radicals having from 1 to 50 carbon atoms, alkenylradicals having up to 50 carbon atoms, alkynyl radicals having up to 50carbon atoms and aryl radicals having up to 30 carbon atoms, in which atleast one hydrogen may be replaced by functional groups, and where oneor both of R₃ and R₄ may be identical or different and are halogen,nitro, nitroso, alkoxy, aryloxy, amido, carboxyl, carbonyl, thio orsulfonyl groups.
 18. A complex of ruthenium of the structural formula I,

where X¹ and X² are identical or different and are each an anionicligand, R¹ and R² are identical or different and are each hydrogen or ahydrocarbon group, where the hydrocarbon groups are identical ordifferent and are selected independently from among straight-chain,branched, cyclic or noncyclic radicals from the group consisting ofalkyl radicals having from 1 to 50 carbon atoms, alkenyl radicals havingup to 50 carbon atoms, alkynyl radicals having up to 50 carbon atoms,aryl radicals having up to 30 carbon atoms and silyl radicals, or R¹ andR² form a ring, where one or more of the hydrogen atoms in thehydrocarbon or silyl groups or both the hydrocarbon and silyl group canbe replaced independently by identical or different alkyl, aryl,alkenyl, alkynyl, metallocenyl, halogen, nitro, nitroso, hydroxy,alkoxy, aryloxy, amino, amido, carboxyl, carbonyl, thio or sulfonylgroups or mixtures thereof, the ligand L¹ is an N-heterocyclic carbeneand the ligand L² is N-heterocyclic carbene of the formulae III-V or anamine, imine, phosphine, phosphate, arsine, carbonyl compound, carboxylcompound, nitrile, alcohol, ether, thiol or thioether and whereinformulae (III)-(V) are

where R₁, R₂, R₃ and R₄ in the formulae III, IV and V are identical ordifferent and are each hydrogen or a hydrocarbon group, where thehydrocarbon groups comprise identical or different, cyclic, noncyclic,straight-chain or/and branched radicals selected from the groupconsisting of alkyl radicals having from 1 to 50 carbon atoms, alkenylradicals having up to 50 carbon atoms, alkynyl radicals having up to 50carbon atoms and aryl radicals having up to 30 carbon atoms, in which atleast one hydrogen may be replaced by functional groups, and where oneor both of R₃ and R₄ may be identical or different and are halogen,nitro, nitroso, alkoxy, aryloxy, amido, carboxyl, carbonyl, thio orsulfonyl groups.
 19. A complex of ruthenium of the structural formula I,

where X¹ and X² are identical or different and are each an anionicligand, R¹ and R² are identical or different and are each hydrogen or ahydrocarbon group, where the hydrocarbon groups are identical ordifferent and are selected independently from among straight-chain,branched, cyclic or noncyclic radicals from the group consisting ofalkyl radicals having from 1 to 50 carbon atoms, alkenyl radicals havingup to 50 carbon atoms, alkynyl radicals having up to 50 carbon atoms,aryl radicals having up to 30 carbon atoms and silyl radicals, or R¹ andR² form a ring, where one or more of the hydrogen atoms in thehydrocarbon or silyl groups or both the hydrocarbon and silyl group canbe replaced independently by identical or different alkyl, aryl,alkenyl, alkynyl, metallocenyl, halogen, nitro, nitroso, hydroxy,alkoxy, aryloxy, amino, amido, carboxyl, carbonyl, thio or sulfonylgroups or mixtures thereof, the ligand L¹ is an N-heterocyclic carbeneand the ligand L² is N-heterocyclic carbene of the formulae III-V or anamine, imine, phosphine, phosphite, stibine, carbonyl compound, carboxylcompound, nitrile, alcohol, ether, thiol or thioether and whereinformulae (III)-(V) are

where R₁, R₂, R₃ and R₄ in the formulae III, IV and V are identical ordifferent and are each hydrogen or a hydrocarbon group, where thehydrocarbon groups comprise identical or different, cyclic, noncyclic,straight-chain or/and branched radicals selected from the groupconsisting of alkyl radicals having from 1 to 50 carbon atoms, alkenylradicals having up to 50 carbon atoms, alkynyl radicals having up to 50carbon atoms and aryl radicals having up to 30 carbon atoms, in which atleast one hydrogen may be replaced by functional groups, and where oneor both of R₃ and R₄ may be identical or different and are halogen,nitro, nitroso, alkoxy, aryloxy, amido, carboxyl, carbonyl, thio orsulfonyl groups.
 20. The complex as claimed in claim 19, wherein theligand L² is phosphine.
 21. The complex as claimed in claim 19, whereinthe ligand L² is P(cyclohexyl)₃, or P(phenyl)₃.
 22. The complex asclaimed in claim 19, wherein X¹ and X² are halide, R¹ and R² arehydrogen or aryl or together form a ring and L² is a phosphine.
 23. Aprocess for preparing acyclic olefins having two or more carbon atoms orcyclic olefins having four or more carbon atoms, in each case of theformula VII

from acyclic olefins having two or more carbon atoms or from cyclicolefins having four or more carbon atoms, in each case corresponding tothe formula VII by an olefin metathesis reaction in the presence of atleast one catalyst comprising the complex as claimed in claim 19 andR′¹, R′², R′³ and R′⁴ in the formula VII are identical or different andare hydrogen or hydrocarbon groups, where the hydrocarbon groups areeach selected independently from among straight-chain, branched, cyclicor noncyclic radicals of the group consisting of alkyl radicals havingfrom 1 to 50 carbon atoms, alkenyl radicals having up to 50 carbonatoms, alkynyl radicals having up to 50 carbon atoms, aryl radicalshaving up to 30 carbon atoms, metallocenyl or silyl radicals, in whichone or more hydrogens may be replaced by a functional group, where oneor more of R′¹, R′², R′³ and R′⁴ may independently be identical ordifferent halogen, nitro, nitroso, hydroxy, alkoxy, aryloxy, amino,amido, carboxyl, carbonyl, thio, sulfonyl or metallocenyl groups. 24.The process as claimed in claim 23, wherein R′¹, R′², R′³ and R′⁴ in theolefins of the formula VII to be prepared form, in pairs, one or moreidentical or different rings.
 25. In a process for olefin metathesisreaction wherein the improvement comprises using a catalyst whichcomprises the complex as claimed in claim
 1. 26. In a process for olefinmetathesis reaction wherein the improvement comprises using a catalystwhich comprises the complex as claimed in claim
 19. 27. An olefinmetathesis process which comprises reacting an olefin with at least onedouble bond in the presence of a catalyst wherein said catalystcomprises the complex as claimed in claim
 19. 28. A process forring-opening metathesis polymer which comprises reacting an olefin withat least one double bond in the presence of a catalyst wherein saidcatalyst comprises the complex as claimed in claim
 19. 29. A process forring-closing metathesis which comprises reacting an olefin with at leastone double bond in the presence of a catalyst wherein said catalystcomprises the complex as claimed in claim
 19. 30. A process for acyclicdiene metathesis polymerization which comprises reacting an olefin withat least one double bond in the presence of a catalyst wherein saidcatalyst comprises the complex as claimed in claim
 19. 31. A process fordepolymerization of an olefin polymer which comprises reacting an olefinwith at least one double bond in the presence of a catalyst wherein saidcatalyst comprises the complex as claimed in claim
 19. 32. An olefinmetathesis process which comprises reacting an olefin with at least onedouble bond in the presence of a catalyst wherein said catalystcomprises the complex as claimed in claim
 1. 33. A process forring-opening metathesis polymer which comprises reacting an olefin withat least one double bond in the presence of a catalyst wherein saidcatalyst comprises the complex as claimed in claim
 1. 34. A process forring-closing metathesis which comprises reacting an olefin with at leastone double bond in the presence of a catalyst wherein said catalystcomprises the complex as claimed in claim
 1. 35. A process for acyclicdiene metathesis polymerization which comprises reacting an olefin withat least one double bond in the presence of a catalyst wherein saidcatalyst comprises the complex as claimed in claim
 1. 36. A process fordepolymerization of an olefin polymer which comprises reacting an olefinwith at least one double bond in the presence of a catalyst wherein saidcatalyst comprises the complex as claimed in claim
 1. 37. In a processfor olefin metathesis reaction wherein the improvement comprises using acatalyst which comprises the complex as claimed in claim
 22. 38. Anolefin metathesis process which comprises reacting an olefin with atleast one double bond in the presence of a catalyst wherein saidcatalyst comprises the complex as claimed in claim
 22. 39. A process forring-opening metathesis polymer which comprises reacting an olefin withat least one double bond in the presence of a catalyst wherein saidcatalyst comprises the complex as claimed in claim
 22. 40. A process forring-closing metathesis which comprises reacting an olefin with at leastone double bond in the presence of a catalyst wherein said catalystcomprises the complex as claimed in claim
 22. 41. A process for acyclicdiene metathesis polymerization which comprises reacting an olefin withat least one double bond in the presence of a catalyst wherein saidcatalyst comprises the complex as claimed in claim
 22. 42. A process fordepolymerization of an olefin polymer which comprises reacting an olefinwith at least one double bond in the presence of a catalyst wherein saidcatalyst comprises the complex as claimed in claim
 22. 43. The complexas claimed in claim 1, wherein R₃ and R₄ are identical or different andare hydrogen, a hydrocarbon group, halogen or a carboxyl group.
 44. Thecomplex as claimed in claim 19, wherein R₃ and R₄ are identical ordifferent and are hydrogen, a hydrocarbon group, halogen or a carboxylgroup.
 45. The complex as claimed in claim 19, wherein the ligand L¹ isa five membered N-heterocyclic carbene.
 46. The complex as claimed inclaim 22, wherein the ligand L¹ is a five membered N-heterocycliccarbene.